The prior art teaches that in closed spaces, such as buildings or other facilities, gas-based fire-suppression or extinguishing systems can be used. Such systems involve injection of a fire-suppressing gas (commonly Argonite or FM200) from an array of high-pressure gas bottles into the closed space to reduce the oxygen level in the air, so as to suppress or extinguish a fire. This may be referred to as flooding the closed space with the fire-suppressing gas. Often, the closed space is also equipped with a ventilation system, for example for cooling. But a ventilation system cannot normally be employed concurrently with a gas-based fire suppression or extinguishing system because the ventilation system typically draws in air from the ambient atmosphere outside the ventilated space. If a fire-suppressing gas is injected into such a ventilation system the incoming air would continually dilute the fire-suppressing gas and reduce its effect.
A ventilation system which draws in ambient air, sometimes supported by evaporative cooling (or other refrigeration-based cooling), can be used for cost-effective, low-energy cooling of buildings and facilities. A typical example of this is the cooling in the information Technology (IT) sector of data centres, server rooms and telecommunication equipment. Such IT equipment or apparatus, which may include computing, telecommunications and similar types of equipment, generates heat during normal operation and needs to be appropriately cooled. In large systems, such as may be found in data centres, server rooms and the like, IT equipment is contained within a system space and ventilation is typically used to assist cooling. This may involve a re-circulating ventilation system, using a refrigeration unit, or a ventilation system drawing in ambient air, which may for example be assisted by refrigeration or by evaporative cooling.
System spaces for housing IT equipment are conventionally designed to meet predetermined standards for cooling, such as the ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers) standards, which set out standard-compliant temperature ranges and recommended temperature ranges to be achieved by ventilation systems. For example, the ASHRAE standards set a compliant temperature range of 10° C. to 35° C., and a recommended temperature range of 18° C. to 27° C., for air supplied by ventilation systems to system spaces containing IT equipment, combined with predetermined air flow rates.
A data centre may contain numerous items of IT equipment, operating independently of one another. In the event of a fire alarm or fire, only one or some of the items of IT equipment may be affected by the fire. In reacting to the fire alarm or suppressing the fire, it is therefore important to continue to provide cooling (ventilation) to the unaffected items of IT equipment, so that they can continue normal live operation. In a re-circulating, refrigeration-based, cooling system, a fire-suppressing gas can be injected into the system space to reduce the oxygen concentration, while air re-circulation and refrigeration can continue, in order to cool the operational IT equipment. However, in a ventilation system which draws air from the ambient atmosphere, if the oxygen concentration in the system space is to be reduced, it is necessary to close the ventilation system's air inlet when injecting the fire-suppressing gas in order to avoid diluting the fire-suppressing gas. But closing the air inlet prevents the normal operation of the ventilation system to cool the IT equipment, and so there is a risk that the operational IT equipment will overheat. In conventional data-centre systems and similar IT systems, this problem is addressed by installing a refrigeration-based cooling system in the system space (in addition to the ambient-air ventilation system). The refrigeration-based cooling system is inactive during normal operation of the IT systems, and is only activated during a fire alarm or fire, for cooling the system space when the normal air inlet is closed and ambient air cannot be drawn into the system space for cooling. The provision of a refrigeration-based cooling system solely for use in the event of a fire alarm or fire disadvantageously significantly increases the capital cost, complexity and maintenance cost of the infrastructure for such an IT system.